Interacting with distributed systems may take place in a variety of ways. In an Ethernet network, for example, devices are interconnected by the network and accessible to each other in a straightforward way. In the Internet, in contrast, messaging between devices may take place using internet protocol, IP, addressing and domain names. For example, a node may inquire for an IP address of a desired correspondent node based on a known domain name. Such an inquiry may be addressed to the domain name system, DNS. By updating to DNS, even changing IP addresses can be handled without interrupting connectivity.
Sensor networks may comprise sensor nodes interconnected with each other. Sensor nodes may be configured to communicate with each other and to provide sensor information to further nodes not comprised in the sensor network. To this end, a sensor network may have an internal addressing system distinct from an external IP network. At least one node in the sensor network may be either addressable from outside the sensor network, or be configured to provide information to a node external to the sensor network.
In the Internet of Things, IoT, scheme it is envisioned that a large number of identifiable devices, or nodes, can be communicated with based on an addressing scheme that may depend on the situation and application in question. To enable the large number of identifiable devices being connected to the IoT, addressing in accordance with internet protocol version 6, IPv6, is envisioned instead of the more limited IPv4 as IP addresses might otherwise run out. On the other hand, using network address translation, NAT, IPv4 addressing may be extended and the scarcity of IPv4 addresses alleviated, with an impact on usability that may vary depending on what kind of communication is desired.
Some IoT nodes are foreseen to have limitations in hardware and energy resources. For example, such nodes may be furnished with only limited memory capacity, they may operate on small batteries and/or they may have only modest processor capability. To enable their use in networking, protocols such as the constrained application protocol, CoAP, have been designed. CoAP has been standardized by the Internet Engineering Task Force.